Technical challenges for the Brazilian GP

The season finale this year is set to be a thriller, with the driver's championship still open and the weather possibly intervening with a straightforward race. However, that doesn't mean the technical challenges are present, so here is what Interlagos looks like to the engineers.

Interlagos has the highest altitude of the year, an average of 800m above sea level. As the altitude increases the air pressure drops and the air is thinner with a lower oxygen content. With less oxygen available for the fuel to burn, power output drops. For every 100m the engine loses around 1% of its potential power output, meaning the engines will produce around 8% less power than at a sea-level race such as Korea.

In addition to the high altitude, the rise and fall of the local topography gives a total elevation change of 150ft over the course of a lap. Correspondingly the local ambient pressure varies by approximately 5 mbar so the engine will require approximately 0.5% less fuel at the peak of the circuit than at the lowest point.

Interlagos has however one of the lowest fuel consumption rates per kilometre due to the high altitude and lower air density so a lower fuel level may also be used to achieve the optimum air-to-fuel ratio.

The weather over the weekend is scheduled to be wet, which will affect the power settings available to drivers as the high water content in the air will again reduce the amount of oxygen available to burn. To combat any further loss of power, engineers may use richer engine and fuel mixes. There are fewer risks involved in doing this at Interlagos than normal since the lower ambient pressure gives the internals of the engine an easier life.

There have already been several off camber corners this season where the lubricants are ‘squashed’ to one side, but there are no more obvious examples of this phenomenon than the first corner of Interlagos, the Senna S. This off camber left hander drops sharply downhill, putting the cars an angle of approx 30°. Higher fuel and lubricant levels may be used to safeguard against any momentary stall as the fluids drop suddenly to one side of the tank, and fuel collectors are often designed with this corner in mind as it is the most severe of the season.

Interlagos is the bumpiest permanent track of the year due to the intense weather conditions, relative lack of use and location. The large bumps can make the car temporarily ‘take off’. Even if it’s just for a second, with no load running through the wheels the engine suddenly hits the rev limiter, which puts the internal parts under huge stress.

Good to know:
- From the last 10 races at Interlagos, 6 saw at least one safety car deployments
- In the last 10 races, only twice did the polesitter win the race (2006, 2008)
- Fuel consumption and fuel effect are relatively low, compared to the majority of the season
- Kerbs are not a problem
- The Brazilian GP is a hard race for the drivers with many compressions and a long time spent dealing with lateral loads which applied on the opposite side to most circuits
- Top speed can be reached in T1 or T4 depending on wind condition
- First gear is not used on the track
- Maximising traction is usually the main balance issue
- This is a very "driven" track with fast turns which translate into not very demanding braking zones. Of the 7 braking zones on the circuit, none create any particular difficulty for the braking system, which is able to cool adequately in spite of the fact that the driver presses the brake pedal for about 13% of the time